# NTSB ERA14LA223: Messerschmitt-Bolkow-Blohm BK 117, N504TJ, Hamburg, NY, May 4, 2014 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: May 4, 2014, 17:40 local (21:40 UTC) - Place: Hamburg, NY - Coordinates: 42.694721, -78.773612 - Nearby events: https://openairdocs.org/map.md?lat=42.6947&lon=-78.7736&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed, report February 3, 2016 - Report: Approved by Office Director - NTSB office: Eastern Region Aviation - Parties: FAA, Airbus Helicopters, Airbus Helicopters Inc. - NTSB case key (mKey): 89167 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA14LA223 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/89167/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=89167 - Page: https://openairdocs.org/ntsb/ERA14LA223 ## Probable cause Wear in the left cabin door assembly parts, which resulted in the door partially opening in flight, dislodging from the lower door track assembly, and then separating from the helicopter. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Doors: passenger/crew doors](https://openairdocs.org/ntsb-findings/01035210): Aircraft › Aircraft structures · Fatigue/wear/corrosion (probable cause); cases with it: [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01035210/cases.md) - [Doors: passenger/crew doors](https://openairdocs.org/ntsb-findings/01035210): Aircraft › Aircraft structures · Incorrect service/maintenance (probable cause); cases with it: [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01035210/cases.md) - [Doors: passenger/crew doors](https://openairdocs.org/ntsb-findings/01035210): Aircraft › Aircraft structures · Failure (probable cause); cases with it: [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01035210/cases.md) - [Inspection: scheduled/routine inspection](https://openairdocs.org/ntsb-findings/02061520): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [All aircraft, 167 cases](https://openairdocs.org/ntsb-findings/02061520/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Prior to flight: Aircraft maintenance event](https://openairdocs.org/ntsb-events/040); cases with it: [All aircraft, 484 cases](https://openairdocs.org/ntsb-events/040/sequence.md) - [Enroute-cruise: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) (defining event); cases with it: [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The pilot reported that, during a repositioning flight of the emergency medical services helicopter and while at cruise altitude, the flight nurse notified him and the paramedic that the left cabin door had partially opened. As the flight nurse and paramedic were attempting to close the door, it dislodged from the lower track assembly, pivoted up, and struck the main rotor system; the door subsequently separated from the helicopter. The pilot then initiated a forced landing to a field. Examination of the door assembly revealed that both of the lower door's bracket guides and the aft lower catcher and guide assemblies were worn and that the door's upper sliders were worn down to their minimum tolerances. The Airplane Maintenance Manual states that, if one of the two sliders does not meet the minimum tolerance, "both sliders must be replaced with new ones." A review of the maintenance logbook revealed that the door assembly had been inspected 127 hours before the accident in accordance with an alert service bulletin but that no anomalies with the door assembly were noted at that time. ## Factual narrative On May 4, 2014, about 1740 eastern daylight time, a BK-117 A-4, N504TJ, was substantially damaged while in cruise flight near Hamburg, New York, after a cabin door separated from the helicopter and struck the main rotor blades. The commercial pilot and the two passengers were not injured. The helicopter was registered to and operated by Mercy Flight Incorporated under the provisions of 14 Code of Federal Regulations Part 91 as a positioning flight. Visual meteorological conditions prevailed and no flight plan was filed. The flight departed Women and Children's Hospital Heliport (7NK9), Buffalo, New York, at 1730. According to the pilot, the helicopter was in cruise flight at an altitude of 3,000 feet mean sea level (msl). The flight nurse alerted the pilot and flight paramedic that the left sliding door had opened several inches. The flight nurse and the flight paramedic then attempted to close the door, but as the pilot reduced the forward airspeed the lower portion of the door dislodged from the lower track assembly and pivoted up, striking the main rotor system. Upon contact with the main rotor system the door departed the airframe. The pilot initiated a forced landing to a baseball field, and the door was recovered for further examination. The pilot reported that the flight paramedic completed the walk-around and inspected doors for closure prior to sitting in the co-pilot seat and securing that door. The door caution lights were extinguished prior to takeoff and did not illuminated until the left sliding door opened at cruise altitude. A cursory examination of the door assembly by the operator revealed that the door was broken into several pieces. The airframe latch assembly did not reveal any anomalies. The door latch and spring assembly was examined and it was questioned by the operator that it may have failed. The operator also stated that they did not have engineers on staff to examine the door assembly latch. The left cabin door and the main rotor blades were examined at Airbus Helicopters Incorporated under supervision of the Federal Aviation Administration. The examination revealed that the main rotor blades were substantially damaged and the doors upper sliders exhibited excessive wear. Both lower door bracket guide assemblies were damaged from impact, and partially separated from the composite door structure. Both guide brackets on the door assembly were worn. The aft lower catcher and guide assemblies revealed impact damage, and were partially separated from the door structure. The catcher and guide assemblies revealed a 45 degree worn away section at the forward catch. Although the door latch was impact damaged, it appeared to operate properly. In accordance with Chapter 21, page 16B, of the Maintenance Manual MBB-BK117, the caution sections states, "if the minimum measure of 1.0 + 0.5 mm is not reached on one of the two sliders, both sliders must be replaced with new ones." The sliders were at the minimum tolerance level of 0.5mm. A review of the logbook excerpts revealed that the door assembly was inspected 127 hours prior to the accident in accordance with Alert Service Bulletin MBB-BK117 No. ASB-MBB-BK117-20-111. No anomalies were noted with the door assembly at the time of that inspection. ## Aircraft - Registration: N504TJ (not matched to a registry record) - Reported make and model: MESSERSCHMITT-BOLKOW-BLOHM BK 117 (A-4) - Category: Helicopter - Serial number: 7138 - Year built: 1971 - Airframe hours: 11735 - Engines: Honeywell LTS-101-650B1 550 horsepower turbo shaft; Honeywell LTS-101-650B1 550 horsepower turbo shaft - Damage: Substantial damage - Flight: Positioning, Part 91 - Operator: Mercy Flight Inc - Registered owner: Mercy Flight Inc - Airworthiness certificate: Standard, Transport - Last inspection: 100 hour, April 14, 2014 - Departed: 7NK9, Buffalo, NY - Destination: 5NK4, Olean, NY - Flight plan: Company VFR - Equipment: Unknown ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 45; injuries: none; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane, helicopter; medical: class 2, without waivers/limitations; last flight review April 21, 2014; seat: right; restraint: 3-point; flight hours: 3,310 total, 365 in this make and model, 3,260 as pilot in command, 32 in the last 90 days, 12 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 340° at 10 knots - Visibility: 10 statute miles - Lowest ceiling: 4,200 ft overcast - Temperature: 50 °F, dew point 37 °F - Altimeter: 29.84 inHg - Observed at: BUF, 15 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Incident 20140504008879I](https://openairdocs.org/incident/20140504008879I), May 4, 2014: Messerschmitt-Bolkow-Blohm BK 117 A-4, Boston, NY, Minor damage. On may 4, 2014 at approximately 1800 EDT mercy flight of western new york helicopter N504TJ, an mbb bk 117-A4, made an emergency landing in a baseball field in… ## Docket (10 files) The files NTSB released with the investigation on December 21, 2015, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=89167. 8.7 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40435133&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - FAA Inspector Statement (item 2, .PDF, 23 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40435134&FileExtension=.PDF&FileName=FAA%20Inspector%20Statement-Master.PDF - Main Rotor Blade Report (item 3, .PDF, 2.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40435135&FileExtension=.PDF&FileName=Main%20Rotor%20Blade%20Report-Master.PDF - Maintenance and Inspection Excerpts (item 4, .PDF, 848 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40435136&FileExtension=.PDF&FileName=Maintenance%20and%20Inspection%20Excerpts-Master.PDF - Ops Spec and ASB Compliance (item 5, .PDF, 1000 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40435137&FileExtension=.PDF&FileName=Ops%20Spec%20and%20ASB%20Compliance-Master.PDF - Alert Service Bulletin MBB-BK117 (item 6, .PDF, 160 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40435138&FileExtension=.PDF&FileName=Alert%20Service%20Bulletin%20MBB-BK117-Master.PDF - AHI Door Exam N504TJ (item 7, .PDF, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40435139&FileExtension=.PDF&FileName=AHI%20Door%20Exam%20N504TJ-Master.PDF - N504TJ Damaged Door Photos (item 8, .PDF, 6 photos, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40435140&FileExtension=.PDF&FileName=N504TJ%20Damaged%20Door%20Photos-Master.PDF - BK117 Inspection Schedule (item 9, .PDF, 224 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40435141&FileExtension=.PDF&FileName=BK117%20Inspection%20Schedule-Master.PDF - BK117 MM 12-4 to 21-11 Maintenance Manual Excerpts and Control Measurements (item 10, .PDF, 359 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40435142&FileExtension=.PDF&FileName=BK117%20MM%2012-4%20to%2021-11%20Maintenance%20Manual%20Excerpts%20and%20Control%20Measurements-Master.PDF From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.